In 1987, three independent research teams reported a population of T cells expressing a moderate intensity of TCRαβ and having no expressions of CD4 and CD8[1-3], respectively; in 1990, Sykes reported a cell subpopulation which expresses both NK1.1 and TCRαβ[4]. In 1995, “NKT” cell was firstly used as a proper noun, and it especially refers to a subpopulation of T cells expressing NK1.1 (mouse, CD161c) marker[5]. According to the CD1d restriction and the TCR diversity of NKT cells, Godfrey classified mouse NKT cells into three types of populations: Type I NKT cells, Type II NKT cells and NKT-like cells. Type I NKT cells were classified as a population of NKT cells that can recognize CD1d presented α-Galcer lipid antigens. Type II NKT celsl can recognize CD1d presented lipid antigens other than α-Galcer. NKT-like cells include other NKT cell subpopulations other than Type I NKT cells and Type II NKT cells. Among them, most extensive researches have been made on the immunological features and functions of the Type I NKT cell which is also known as a classical NKT cell; at present, most of NKT cells mentioned in the literatures are actually the classical NKT cells. With the development of CD1d tetramer technology as well as the establishment of CD1d-deficient transgenic mice, the current researches on NKT cells mostly focused on the classical NKT cell (i.e., Type I NKT cell). However, Type I NKT cell is only one population of NKT cell, and more than 50% of NKT cells are NKT-like cells[6]. The development of NKT-like cell does not depend on CD1d molecules, and yet NKT-like cell expresses a variety of TCR chains. However, there are few researches on the NKT-like cells at present. Existing researches showed that the NKT-like cells have an antitumor effect. A population of NKT-like cells which is not dependent on CD1d molecules has been found in β2 microglobulin deficient mice, and these cells can be able to kill many kinds of tumor cells in vitro[7].
Chinese patent application No. 201510494011.4 relates to a new NKT-like cell subpopulation and use thereof in the treatment of tumor. The NKT-like cell subpopulation comprises CD8+ NKT-like cells which were demonstrated as cells having a potent anti-tumor effect in NKT-like cells. In the application, the autologous lymphocytes were isolated from a subject and then NKT-like cell subpopulation was sorted out from the lymphocytes. The sorted NKT-like cell subpopulation was expanded by the addition of a cytokine or a combination of cytokines. The expansion of sorted CD8+ NKT-like cells was achieved by the addition of a specific cytokine or a specific combination of cytokines in CN 201510494011.4. However, the application did not mention other means or possibilities of the activation and expansion of CD8+ NKT-like cells in vitro.